title: Eu-actinin, a new structural protein of the Z-line of striated muscles.
abstract: A new protein component of the Z-line of striated muscles was isolated from chicken breast muscle. This protein has been designated as eu-actinin because of its close similarity in polypeptide molecular weight to actin. Eu-actinin was extracted from myosin-removed myofibrils at low ionic strength at pH 6.5 and purified by column chromatography on Sepharose 4B and DEAE-cellulose. Although the polypeptide molecular weight of eu-actinin measured by SDS-polyacrylamide gel electrophoresis is similar to that of actin, other physico-chemical properties of eu-actinin definitely differ from those of actin. The isoelectric point of eu-actinin was more acidic than that of actin. The amino acid composition of eu-actinin was found to be different from that of actin or those of other muscle structural proteins. The results of analytical gel filtration on Sepharose 4B indicated that eu-actinin forms dimers through non-covalent bonding under aqueous conditions. Eu-actinin has a low axial asymmetry under low-salt conditions, as judged from its intrinsic viscosity ([eta] = 6.4 ml/g for the dimer state) and exhibits a tendency to undergo self-association with increasing ionic strength. Interactions of eu-actinin with other muscle proteins were examined by the affinity column technique. It was shown that eu-actinin binds to actin and alpha-actinin. Eu-actinin exhibited strong seeding ability for the polymerization of actin. Antibody to eu-actinin was raised in a goat and purified by affinity chromatography. The specific antibody against eu-actinin did not form precipitine lines with actin or alpha-actinin. Immunofluorescence studies revealed that eu-actinin is localized at the Z-line of myofibrils. The FITC-conjugated antibody to eu-actinin also stained the Z-lines of rabbit skeletal muscle and chicken cardiac muscle. Therefore, it was concluded that eu-actinin is a new, ubiquitous constituent of Z-lines of striated muscles.
mesh_terms: D000185:Actinin / Q000302:isolation & purification*; D000199:Actins; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002645:Chickens; D004591:Electrophoresis, Polyacrylamide Gel; D005779:Immunodiffusion; D046911:Macromolecular Substances; D008970:Molecular Weight; D009124:Muscle Proteins / Q000302:isolation & purification*; D009132:Muscles / Q000032:analysis*; D009210:Myofibrils / Q000032:analysis; D009994:Osmolar Concentration
chemical_list: D000199:Actins; D000596:Amino Acids; D046911:Macromolecular Substances; D009124:Muscle Proteins; D000185:Actinin